Question

我有两个查询，如果值为1，则我有一个值，如果值为2则接第一个查询将执行。我怎样才能实现这一点，我的查询是

如果值为1，则查询一个

SELECT  count (CASE WHEN col1 = 9 THEN 1 ELSE 0 END  )AS "matches" ,
              CAST( CASE WHEN col1 = 9 THEN 1 ELSE 0 END  AS VARCHAR(10)) + ' / 1' AS "match by"
              FrOM table a
              where ( SELECT  CASE WHEN col1 = 9 THEN 1 ELSE 0 END  AS "matches"  )  >= 1
              group by  ( CASE WHEN col1 = 9 THEN 1 ELSE 0 END ) 
              )

如果值2

，则查询2

 SELECT  count (CASE WHEN col1 = 9 THEN 1 ELSE 0 END    +  
                CASE WHEN col2 = 10 THEN 1 ELSE 0 END  
                )AS "matches" ,
                CAST( CASE WHEN col1 = 9 THEN 1 ELSE 0 END 
                +  CASE WHEN col2 = 10 THEN 1 ELSE 0 END AS VARCHAR(10)) + '/ 2'  AS "match by"
                FrOM table a
                where ( SELECT  CASE WHEN col1 = 9 THEN 1 ELSE 0 END + 
                 CASE WHEN col2 = 10 THEN 1 ELSE 0 END AS "NUM_OF_MATCHES"  )  >= 1
                group by  ( CASE WHEN col1 = 9 THEN 1 ELSE 0 END+ 
                 CASE WHEN col2 = 10 THEN 1 ELSE 0 END )

我已尝试使用案例，但它无效

我想if value = 1然后第一个查询将运行，if value = 2然后第二个

虽然两个查询都做同样的工作，但是如果值为1则col1逻辑只接受col1，如果value为2则接受col1和col2，如果value为3则接受col1 col2和col3直到6 col

Answer 1

你还在使用CASE Statement，为什么不尝试使用IIF Statement，IIF Statement比CASE Statement更有效率和快速。

e.g。

select IIF(1=1, (your desired column1),(your desired column2)) as matches

您还可以在CASE语句等单一查询中使用嵌套的IIF语句。

select IIF(1=1, (IIF(2=2, (your desired column1),(your desired column2))),(your desired column3)) as matches.

两个选择语句与案例

1 个答案: